PD-1 expression contributes to the functional impairment of NK cells in patients with B-CLL

Chronic lymphocytic leukaemia (B-CLL) is associated with immune suppression and functional impairment of NK cells, due partly to the reduced expression of activating receptors. We studied the profile of inhibitory checkpoint receptor expression on NK cells from patients with B-CLL. Single, dual and triple expression of the checkpoint receptors PD-1, CTLA-4, LAG-3 and CD96 was increased in patients compared to age-matched healthy controls. PD-1pos cells were present within the late differentiated CD56dim NK pool and showed strong downregulation of all activatory receptors whilst transcriptional profiles revealed a profile of strong receptor signalling. PD-1pos NK cells demonstrated impaired cytokine production and degranulation following target engagement and transfection of PD-1 into NK cell lines directed suppressed cytotoxic function. Importantly, blockade of PD-1:PD-L1 engagement acted to partially reverse these functional defects. These results reveal expression of inhibitory checkpoint receptors to be a new mechanism of NK cell dysfunction in patients with cancer and indicate a potential therapeutic role for single or combinatorial checkpoint blockade to boost immune function in patients with B-CLL. Single Cell RNA profiles of NK cells, positve for PD-1 and Negative for PD-1

慢性淋巴细胞白血病（B-CLL）与免疫抑制及自然杀伤细胞（NK cells）的功能损伤密切相关，其部分诱因是活化受体的表达水平降低。本研究针对B-CLL患者体内NK细胞的抑制性检查点受体表达谱展开分析。与年龄匹配的健康对照组相比，患者体内检查点受体程序性死亡受体1（PD-1）、细胞毒性T淋巴细胞相关抗原4（CTLA-4）、淋巴细胞活化基因3（LAG-3）及CD96的单阳性、双阳性与三阳性表达水平均显著升高。PD-1阳性细胞分布于晚期分化的CD56dim NK细胞亚群中，其所有活化受体均呈现显著下调；转录组谱分析显示该群体存在强烈的受体信号激活特征。PD-1阳性NK细胞在接触靶细胞后表现出细胞因子产生与脱颗粒功能受损；而将PD-1转染至NK细胞系后，可直接抑制其细胞毒活性。值得注意的是，阻断程序性死亡受体配体1（PD-L1）与PD-1的结合可部分逆转上述功能缺陷。本研究结果表明，抑制性检查点受体的表达是癌症患者NK细胞功能异常的全新机制，同时提示单药或联合使用检查点阻断疗法可用于增强B-CLL患者的免疫功能，具备潜在临床治疗价值。包含PD-1阳性与PD-1阴性NK细胞的单细胞转录组谱。